1. Field
This invention relates to apparatus for disassembling stacked members from a pump impeller shaft. More particularly, the invention is directed to an apparatus for easing the disassembly of stacked members from a pump impeller shaft wherein those members have been subjected to compressive loading.
2. State of the Art
Many types of pumps employ shafts in their construction. Oftentimes structural members are stacked or otherwise mounted on these shafts to accomplish various mechanical purposes. Due to the operational nature of these pumps and the uses made of such shafts, frequently the members shafts are subjected to compressive loading. The application of loading forces to the various structural members may cause these members to be difficult to remove for servicing.
For example, in a conventional pump, an impeller is attached to its support shaft by means of a threaded connection. The impeller hub is threaded on the end of the shaft until it bottoms out against a shaft sleeve and/or shaft shoulder. During the operation of the pump, the torque forces which were initially applied in mounting the hub onto the shaft are supplemented by those forces resulting from the impeller pumping torque. Tightening torque is initially applied mechanically and increases during pump operation, e.g., motor shaft torque transmitted to oppose impeller fluid pumping torque. This results in further screwing of the impeller against the shaft shoulder or shaft sleeve. The result is that compressive forces are set up in the threads, shaft shoulder or shaft sleeve and the assembly acts as a preloaded spring with a loaded length shorter than the free length.
Recognizing that impellers, or pumps in general, require maintenance for their proper continued operation, and furthermore, recognizing that many of the component parts of the pump assembly itself must be removed from the pump for purposes of servicing and maintenance, it becomes apparent that oftentimes the pump assembly must be disassembled in order to permit proper servicing. In those environments wherein the above-described force applications cause the impeller or associated sleeves and the shaft shoulder to become compressively loaded, this disassembly may be very difficult. Observably, the repairman must overcome the effects of relatively high compressive load forces in order to separate the various structural members of the pump assembly.
The conventional method for disassembling an impeller from its support shaft is to apply an impact torque force to a special wrench which has been attached to the support shaft and locked into a keyway associated therewith. The impeller itself must be locked into position and rendered immobile in order to apply the torque force to the support shaft. Due to its particular configuration, the impeller presents a rather difficult structure to immobilize. A further drawback to the conventional method is the fact that the application of impact wrench loads are often detrimental to shaft bearings.
Efforts have been made in the art to provide a collar-type arrangement which is positionable on the shaft between the members being compressively loaded, e.g. the impeller and the shaft shoulder. This collar-type arrangement has been adapted to relieve the compressive loads which may have been applied to the structural members stacked on the pump shaft. In this approach it has been customary to construct a collar having a plurality of segments which may be individually removed radially from the shaft by jacking, prying, or impacting.
The use of a multi-segmented collar assembly has been found to present certain disadvantages. In utilizing such an assembly, the first few segments are relatively easily removed from the collar assembly. As the shaft-mounted segments decrease in number, the forces being applied to the remaining segments increase sufficiently that upon the repairman reaching the last-in-place segment, that segment is then subjected to an axial compressive load which requires an excessively large removal force in order to extract it from positioning on the pump shaft. Understandably, the increase in the compressive load on this last segment and the magnitude of the force required to remove it increases the likelihood that the last segment will be deformed or otherwise damaged during the removal process.
Another disadvantage is that the use of multi-segmented collar assemblies involves the use of number of segments which may be easily lost or misplaced during the removal and/or installation process.
The environments in which pumps are called on to function oftentimes are chemically or environmentally hazardous. In such environments, the various pump components are subjected to harsh and corrosive chemical substances. The use of pump assemblies in such environments can effect the operation of the conventional multi-segment collar assembly in that the environment may contribute to the various segments of the collar assembly being rendered inseparable from one another. As a result, it is difficult to separate one segment from another in order to properly follow the disassembly method for removing the collar assembly.
A fourth complication attending the use of multi-segment collar assemblies is the fact that these assemblies present a less than smooth outer surface. When the collar assemblies are rotated during the operation of the pump, they may present a hazard to the pump operator. More specifically, the outer surface of the segmented design is often times interrupted by the structural features of fasteners or impact lugs which are required for the proper operation of the multi-segment collar assembly. These collar assemblies often must be located proximate to the pump packing adjustments where shaft leakage containment corrections are made by the operator. Since the operator regularly must be near or in the area of the plural segmented collar assemblies, the rotation of the assembly during the pump's operation, together with the less than uniform surface of the collar assembly may present a hazard to an operator in that the non-uniform surface may catch or otherwise contact the clothing or actual person of the operator.
In view of the present state of the art, there continues to be a pressing need for a collar assembly adapted for facilitating the disassembly of various stacked members on a shaft which have been subjected to high compressive loading. This new collar assembly should remedy many of the less than favorable structural characteristics of the conventional plural segmented collar assemblies.